The goals of this project are: (1) To identify additional receptors involved in HIV cell entry and fusion. (2) To develop sensitive assays to measure HIV-cell-binding and cell-fusion, (3) To use these assys for the evaluation of anti-HIV theraputic agents (e.g. soluble CD4, combination monoclonal antibodies). We recently demonstrated that the newly identified HIV-1 co-recptors (belonging to the cytokine receptor family) , cann associate with surface CD4 molecules after the addition of HIV-1 envelope to human cells. Multiple mabs are currently being tested for their ability to block (or augmet) the HIV-1 co-receptor function of these chemokine receptors, and in parallel, their potential negative effects on the normal functions of these receptors. Assays developed will be used in the evaluation of the potency of anti-viral agents directed at blocking of HIV-1 cell entry and cell-to-cell transmission.